Chain of Custody Laboratory

7/28/2019 Chain of Custody Laboratory

http://slidepdf.com/reader/full/chain-of-custody-laboratory 1/50

BY

Ashraf Mahmoud Emara

Professor of Clinical Toxicology

Forensic Medicine and Clinical Toxicology

Department

Faculty of medicineTanta university



Objectives: By the completion of the lecture the audience

should answer the following questions:- What is meant by chain of custody?- How to apply the chain of custody?- What are the biological materials that are usedfor testing and how to choose?



What is meant by chain of custody?

It is the ability to trace and

safe guard the samplethrough all steps from

collection, analysis, tofinal report of the result .



How to apply the chain of custody?

1- Sample(s) collection.

2- Personnel and security .

3- Storage and use of sample.



Collection of sample Written consent from donor.

Identification of the donor.Type of sample.

Problems arise from storage,transfer and standards used totest.



• Sample ID

•

Date and time• Preservation

• Analysis required

• Name of collector


Chain of custody sheet or form:

Each time possession of samples is transferred, both theperson delivering the sample and the person receiving thesample sign the form and record the date and time on the

COC.




•Suspected agents.

•Suspected dose.•Time of ingestion and sampling.

•Clinical presentation.•Location of the patient.

An accompanied analytical

toxicology request



























No Test Arrival of sample without chain of custody form.

Red tamper seal is missed or broken.

chain of custody form is not signed by either collectoror subject.

Sample ID on label and chain of custody form do notmatch.

No initials by the subject on Red tamper seal. White sample ID label overlaps the Red tamper seal.



Each time possession of samples is transferred, boththe person delivering the sample and the person

receiving the sample sign the form and record the dateand time on the form.





In clinical cases: the presence of drug at

the time of original collection is usually desired,hence any later collection is worthless.

1- Sample(s) collection:

In forensic cases : the specimens collection is

very important since there is rarely an opportunity torecollect specimens. Bodies have usually sent out of

mortuary.



Choice of specimens

It depends on:

- The purpose of the testing-The instrumentation and The methodology



Choice of specimens

In situation:

live persons, the specimens are:• Blood (for plasma or serum) for quantitative analysis.

• Urine for qualitative.

• Gastric contents may be for diagnosis of toxicities as phosphides

rodenticides or for medico-legal causes.• Other specimen as saliva, hair, nail and sweat are being

increasingly used as alternatives to plasma and urine and can be

provide additional information.

In dead persons:• All samples that can be collected from living persons.

• Tissues.



Specimens

1- Blood2- Urine 3- Gastric

4- Liver and other tissues specimens5- Bile6- Vitreous humor7- Hair8- Sweat9- Saliva



Indications: (quantitative analysis)

Analysis for recent ingestion.

Therapeutic drug monitoring.

In clinical cases it is taken from the veins in the arms.

In post mortem is preferentially taken from femoral

region to avoid contamination from abdominal fluidsand contents and to reduce the artefactual due toredistribution.

Blood

CHAIN OF CUSTODY



Volume : 5-20ml.

Serum: When whole blood is allowed to stand (15

min, room temperature) in a plain tube (noanticoagulant) a clot forms that will retract sufficiently to allow serum to be collected. For many analysesserum is preferred to plasma because it produces less

precipitate (of fibrin) on freezing and thawing.

Blood

CHAIN OF CUSTODY



ANTICOAGULANTS

EDTA

Oxalate

Heparin

Sodium Citrate

Sodium Fluoride/Potassium Oxalate

Blood

CHAIN OF CUSTODY



ANTICOAGULANTS

EDTA (Ethylenediaminetetraacetic acid):

Two forms are used: The tripotassium salt(K3EDTA), and the disodium salt (Na2EDTA ).

0.5 -2.0 mg EDTA per ml of blood will preserveblood excellently for at least 6 hours. Refrigeration

will extend the preservation to 24 hours.

Blood

CHAIN OF CUSTODY



ANTICOAGULANTS

Oxalate

A mixture of dry ammonium oxalate andpotassium oxalate in the ratio of 3:2.

2 mg of the mixture will prevent coagulation in 1ml of blood.

Blood

CHAIN OF CUSTODY



ANTICOAGULANTS

Heparin

The optimum concentration is 0.1 to 0.2 mg/ml of blood.

It interferes with the formation and/or activity of thrombin and the activity of clotting factors IX, X,

XI, XII.

Blood

CHAIN OF CUSTODY



ANTICOAGULANTS

Sodium citrate

The standard concentration is 1 part 3.8% solutionto 9 parts of blood.

Sodium fluoride - Potassium oxalate mixture

4 parts sodium fluoride + 5 parts potassium

oxalate. Optimum concentration is 1 mg of the mixture per

1 ml of blood.

Blood

CHAIN OF CUSTODY



Disadvantage:

Blood concentration of drugs are

often low and short time limited.Not all blood levels correlate with

clinical effects.

Basic drugs have large of distribution, so urine ispreferable.

Blood

CHAIN OF CUSTODY



Collected over interval of time (1, 4, or24 hours.

Clean, early-morning, fasting sample

is the most concentrated one.

Urine

CHAIN OF CUSTODY



Advantages:- Concentrations of drugs or their are

usually much higher than in blood.

- The drugs may be detected for longertime.

- Easy sample preparation and analysis.

- Volume collected can easily exceed 20ml.

- Non invasive technique for collection.

Urine

CHAIN OF CUSTODY



Disadvantages:- Can easily adulterated, diluted or

substituted.

- A recently ingested drug may not yet havebeen excreted into urine, and if it providelittle information about the amount

present in blood. So indicated forscreening of drug of abuse and sportstesting.

- Bacterial contamination (refrigeration).

Urine

CHAIN OF CUSTODY



Advantages:

- A very useful indicator of drug exposure.

- The presence of drug in higher dose than thetherapeutic dose is a good evidence of recent drug

ingestion.- The whole content of the stomach in deceased person

are provided to the laboratory.

Disadvantage:

- Recent ingestion may be misdiagnosed by re-excretion of the drug in stomach e.g. morphine andheroin.

Gastric contents CHAIN OF CUSTODY



Advantages:

Liver :

- Easily collected and easily homogenized.

- The primary specimens in decomposed cases

When blood is not available.

Volume :≥ 100 g

Other tissues (skin , fat, muscle and bone) can be

useful when a more accurate estimate of totalbody is required.

Liver and other tissues specimens CHAIN OF CUSTODY



Advantages:- Drugs can persist for longer time than blood

- Drug can appear before it is excreted in urine.

Volume : ~10mL

Collected in:

Plain

Potassium fluoride treated plastic tube

Glass.

Bile CHAIN OF CUSTODY



Advantages:- To establish drugs used many weeks tomonths prior to collection.

- Non invasive for pre-employment analysis.- For metal poisonous metals such as arsenic,

mercury and lead and drug of abuse.

Hair CHAIN OF CUSTODY



Disadvantages:- Contamination from internal or

external source

- Only for quantitative.Weight : at least 50mg

Collected from the back of the head at roomtemperature in a sealed plastic bag




Factors affecting retention and concentration of substances in hair:

1. Physiochemical properties of substances (basic>neutral> acidic)

2. Dose of substance and frequency of administration.

3. Mechanism of incorporation (blood, sweat, sebaceoussecretions)

4. Hair color and type (African and Asian hair show greatestretention)

5. Bleaching of hair and other hair treatment.

6. Decontamination and extraction method for analysis.


C O C S O



- Sweat patches have been used to absorbsweat by keeping in contact with skin for1-5 days.

- Drugs detected in sweat include: BNZ,amphetamines, cocaine, heroin,

morphine, methadone and PCP.

Sweat CHAIN OF CUSTODY

CHAIN OF CUSTODY



- Drugs may enter saliva from bloodby:

- Passive diffusion.

- Ultrafiltration.- Active secretion.

- Specimens can be stored at -20 ˚c, unless analysis is conducted.

Saliva CHAIN OF CUSTODY

CHAIN OF CUSTODY



Disadvantages:- Small mount and little ability to repeat analysis.

- Not all subjects will be able to provide saliva on demand.

- Interpretation of saliva drug concentrations is moredifficult than blood because it differs according to:

- Protein binding

- pKa of drug

- pH of saliva

- Contamination of saliva by recently ingested drug is areal problem.

Saliva CHAIN OF CUSTODY

CHAIN OF CUSTODY



- Quite useful for estimation of alcohol, digitoxinsparticularly when some putrefaction in the body hasoccurred.

- Volume : 1-2mL

- Storage in a 2-5mL plastic, plain or potassium fluoride

preserved containers at -20 ˚c or below.

Vitreous Humour CHAIN OF CUSTODY



• The COC forms accompany the samples to thelaboratory. When the analysis is completed, theCOCs are included with the report.

Personnel and security .

• Specific qualification of the laboratory

personnel .

• Maintaining of a security system so as the

samples are only accessible by authorizedpersonnel.



Storage of sample(s):

- All biological specimens should be stored at 4 °Cprior to analysis.

- For medico-legal purposes specimens should bekept at -20 °C for longer times.



Documents

Chain of Custody Laboratory